Tachometer employing a motion sensing photocell connected as one arm of a bridge circuit



July 30, 1968 R. T. POUNDS 3,395,342

TACHOMETER EMPLOYING A MOTION SENSING PHOTOCELL CONNECTED OF A BRIDGECIRCUIT AS ONE ARM Original Filed Feb. 20, 1961 $5 m aw 4 E WWW 0 NM 3sNC 71 t 4 6i m m I Tawmww W? I a w R w 7 United States Patent 3,395,342TACHOMETER EMPLOYING A MOTION SENSIN PHOTOCELL CONNECTED AS ONE ARM OF ABRIDGE CIRCUIT Richard T. Pounds, deceased, late of Bristol, Ind., byCatherine D. Pounds, sole heir and legal representative, P.O. Box 385,Arlington, Va. 22210 Continuation of application Ser. No. 469,021, June8, 1965, which is a continuation of application Ser. No. 90,578, Feb.20, 1961. This application Oct. 31, 1967, Ser. No. 687,403

8 Claims. (Cl. 324-70) This invention relates to tachometers, andparticularly to a photoelectric speed measuring device for measuring thespeed of a rotating or reciprocating body. This application is acontinuation of application Ser. No. 469,021, filed June 8, 1965, nowabandoned, which was in turn a continuation of application Ser. No.90,578, filed Feb. 20, 1961, also now abandoned.

In many phases of industrial and commercial activities it is frequentlynecessary to measure the rotational speed of machinery. This may beaccomplished in a number of ways, depending upon the nature of thedevice. If the rotating member is supported by a shaft, the end of whichis accessible, speed measurement is sometimes accomplished by means of arevolution counter, the operator observing the number of revolutionsoccurring in a given interval of time and computing the rate per minute.Hand held tachometers of several types are also available for thispurpose, permitting direct reading of rotational speed without thenecessity of making calculations. For obvious reasons all devices of theclass described suffer the disadvantage that physical contact must bemade between the measuring device and the center of the rotating objectwhose speed is to be measured. This is a distinct disadvantage, as theconstruction of many machines and parts thereof is such that contactwith the rotating center either is not possible, or requires that safetyguards or other machine parts he removed. Thi frequently creates acondition hazardous to the operator or observer.

Rotational speed may also be measured without making physical contact byusing a stroboscopic device, which may take the form of a light sourcedesigned to be turned OFF and ON at a controllable rate of speed, theoperator adjusting the rate so as to cause the rotating device to appearstationary. Such devices are usually provided with a calibrated dial,indicating the rate at which synchronization occurs. Other forms of thestroboscope devices are available, all of which utilize the principle ofsynchronizing the motion of one object With that of another anddetermining the speed when relative motion is zero, on the basis ofprior calibration.

Stroboscopic speed measurements suffer a severe limitation in that theycannot be used at low speeds since their principle of operation requiresthat rapidity of motion be greater than the response time of the humaneye. Another disadvantage is that the device being measured must beoperating at a constant speed. Still another disadvantage is thatbecause of harmonic relationship, synchronization may appear to exist atany one of several viewing rates and, therefore, grossly inaccuratemeasurements may result unless the operator is skilled in use of thestroboscope.

Because of the limitations and inconvenience of using commonly availablespeed measuring devices, hazardous conditions are sometimes createdneedlessly in many industrial, commercial and farming operations, sincemeasurements Which should be made to determine whether a particularmachine is operating within its prescribed safe limit are neglected. Oneexample of this situation may be found wherever abrasive wheels are usedin grinding operations. If such wheels are operated at a rotationalspeed greater than that for which they are designed, centrifugal forcesmay cause the wheel to break apart, the pieces of which will beprojected athigh velocity, in a line tangent to the wheels axis ofrotation. The destructive forces of pieces from a shattered abrasivewheel, even a moderate sized one, is sutlicient to pierce steel guards,and is a common cause of fatalities in industrial accidents.

Moreover, wheels operated at improper speeds do not properly accomplishthe grinding operation for which they were designed, and, therefore, arenot only hazardous but are economically wasteful.

Not only is accurate speed measurement important in a wide variety ofindustrial, commercial and farming operations, but the range of speedsvaries considerably. For instance, a tumbling barrel may be operated atspeeds ranging from 10-100 r.p.m., milling cutters may run at speedsranging from about to several hundred r.p.m. Large grinding wheels maybe operated at speeds as low as a few hundred r.p.m., while smaller onesmay be designed .to run at several thousand r.p.m. A free running discgrinder may turn at say 3000 r.p.m., and yet its speed may drop to 1500r.p.m. when properly loaded. Tachometers previously available do notpermit measurements to be taken over the wide range of speeds commonlyencountered and, therefore, several instruments were previously neededif all ranges were to be accommodated.

In order to overcome the limitations of other types of tachometers andspeed measuring devices, I have invented a new and novel tachometer oneobject of which is to provide the user with a readily portableinstrument by means of which rotational speeds may be quickly,accurately and safely measured.

Another object of my invention is to provide means of measuring thespeed of rotating devices, without the necessity of making physicalcontact therewith.

Another object of my invention is to provide means whereby the user mayeasily determine if the instrument is correctly calibrated.

Still another object of my invention is to provide means of easilymeasuring the speed of a bodys rotation on a variable axis, as forinstance, the tub of a centrifugal water extractor or laundry dryer.

A further object of my invention is to provide means of measuring speedof rotating objects Without adding a frictional load to the device beingtested.

A still further object of my invention is to provide means whereby aninstrument with a single calibration range may be used to measure eithervery low speeds or very high speeds with equal accuracy.

Still another object of my invention .is to provide means ofascertaining the variations in speed of a rotating body.

Another object of my invention is to provide means of measuring therepetitive rate of an oscillating or reciprocating body with the sameinstrument ordinarily used for measuring rotating speeds.

Another object of my invent-ion is to provide means whereby the speed ofan object moving in a straight line may be measured in terms of units ofdistance per unit of time.

Still another object of my invention is to provide means of determiningthe repetitive rate of variable intensity light sources, or thefrequency of the exciting source of energy used for powering lightsources whose intensity varies periodically.

In order to accomplish these and other objectives, I have devised asystem of speed measurement whereby a beam of light is caused to bedirected at any convenient point on a revolving body. Markers previouslyattached to the body are of a contrasting color or of a. different shadeof the same color), are successively illuminated by the beam as theobject rotates, reflecting a part of the light back towards theinstrument where it is sensed by a suitable photo-sensitive device.In'turn, the photo-sensitive element causes an electrical impulse to bedeveloped each time a marker reflects light. By using a suitableamplifying circuit and feeding its electrical output into the input of afrequency measuring and indicating network, a workable tachometer may beproduced. Since no physical contact is needed in order to take speedmeasurements, the device is inherently safer to use than ordinaryhand-held tachometers. Also, by proper selection of components,determining the frequency range through which the tachometer is tooperate, a multiple range of r.p.=m. scales becomes immediatelyavailable to the operator, all of which have exactly equal ratios. Thisis more apparent when one considers the device in this fashion: If thedevice is calibrated to cover a basic range of l2,000 r.p.m., this willcorrespond to a frequency range of 0200 cycles per second.

Mechanically driven, hand-held tachometers used commercially, areprovided with multiple range scales, alleviating the latterdisadvantage, but is not an entirely satisfactory solution, since it isdiflicult to maintain an exact calibration relationship between thescales. For example, if a measurement taken on the low speed segment ofthe HIGH range scale of an ordinary tachometer is compared with areading taken on the upper segment of the instruments LOW range scale,the two are apt to be in disagreement and the operator is left in doubtas to the actual speed.

Further objects and features, embodied in the circuitry, are to provide.

(1) An indicator current proportional to rate of rotation;

(2) An indicator current independent of size of signal marker;

(3) A computer circuit to respond only to predominant signal pulses, andto automatically adjust response to the average level of predominantpulses;

(4) Suitable means whereby the time available for recharging thecomputer capacitor will always be sutficiently great to permit thecharge to reach at least 99.9% of the supply voltage, regardless of themagnitude or duration of the exciting pulses;

(5) Suitable means of stabilizing the compute-r circuit so as to insurereliability through a wide range of environmental temperatures; and

(6) Suitable means of insuring that instrument will respond only tosignals whose magnitude is sufficiently great so as to guaranteereliable speed readings.

The arrangement of the elements of the tachometer, in accordance withthis invention, and their method of operation, may be understood uponreference to the accompanying drawings, in which:

FIGURE 1 is a perspective view of the portable tachometer of thisinvention, showing the two lens barrels for the incident and thereflected light beams, and the simple push button to initiate theoperation;

FIGURE 2 is a circuit diagram of the tachometer circuitry; and

FIGURE 3 is a diagram of the metering circuit for a dual rangetachometer of the kind shown in FIGURE 2.

As shown in FIGURE 1, the portable tachometer 10, as seen assembled,comprises a case 12, of box shape, having two barrels or cylinders 14and 16 projecting from the front end 18 to accommodate separate lenses22 and 24. A push button switch 26 (SW1), initiates operation of thetachometer. The scale 28 of the indicating instrument 30 is exposed atthe top of the case 12. For a dual range instrument a switch 32 isprovided to select the metering range desired.

FIGURE 2 shows the circuit diagram. Energy for operation is derived fromtwo batteries 40 and 42. The push button switch SW-l corresponds toswitch 26 of FIGURE 1, and connects both batteries 40 and 42 in circuit.Battery 40 energizes lamp L-l, which, with a suit- W i ,4- ablereflector L-2, in barrel 14, projects an incident light beam 50 at themovable object 55 whose speed is to be measured, and the reflected lightbeam 56 is collected by lens 24 in barrel 16 and focused on photocell60.

The incident light beam 50 should be directed at a surface of themovable object 55 that provides a discontinuity in the reflection, sincethe system is designed to operate on separate light pulses. Otherwise,suitable markers or strips of material 55a may be disposed on themovable object 55, which is shown as a disc 55, in FIG- URE 2, to whichthe markers 55a are applied as narrow radial strips of material toprovide a contrast in reflectivity relative to the material of the disc55. This change in reflectivity provides the differential activation ofthe light cell 60 to initiate generation of an electrical pulse.

The markers may be similarly applied to an object moving in a linearpath, or reciprocated, in a cyclical manner.

Assuming, now, that the reflected beam 56 is broken into pulses or issufliciently undulating to affect the system, the resistance of cell 60will change from high resistance to a low resistance value.

The operating switch 26 or SW-l, which connects lamp L-1 to battery 40,also connects battery 42 to the positive terminal of bus B-2, with busB-l directly connected to the negative terminal of battery 42, so thatbusses B-1 and B-2 serve as negative and positive potentials,respectively of battery 42.

When switch 26, SW-l, is closed the circuits are activated. No readingshould show on the meter unless a signal is received.

Condenser C-7 prevents instantaneous current to the meter.

In addition, voltage-dividers R11, R-13 and R-15 put forward bias onbase of TR-l, and TR-l is put into saturation and closes immediately, toput a shunt across the terminals X and Y, so no current will enter themeter 30.

TR2 should stay open. Proper positive bias is put on the base of TR2 byvoltage-divider R-12, R-8 and back resistance of D-l.

TR-3 should stay open. Proper positive bias is put on the base of TR3 bythe two bridge arms R-7 and R5, as a voltage divider.

No signals are being transmitted. The meter reads zero.

Speed measurement is now desired. The instrument is aimed at therotating device 55. The reflected light beam hits the cell 60 for theduration of the interval that the light beam is on the reflecting marker55a. The cell resistance drops and the bridge is unbalanced. CapacitorC-2 charges negatively for said time interval of reflection, and puts anegative pulse on base of TR-3, suflicient to overcome the positive biason base TR3.

TR-3 goes to saturation, and closes for the duration of said timeinterval pulse. TR3 closed, puts positive pulse from collector onto C-5,which holds TR2 open for duration of that positive pulse. When TR3 goesopen, due to C-2 discharge, TR3 collector goes negative. Therefore C-5goes negative, and puts immediate negative on TR2.

While TR3 was closed, D1 drained positive charges from C-3 and (34.Therefore, the negative pulse from 0-5 was effective immediately on baseof TR2.

TR2 thereupon saturates and closes. That reduces forward bias on TR-l,whose collector goes more negative and regenerates more negative at baseof TR2 to contribute to fast TR2 saturation.

TR1 goes open to cut off and puts voltage pulse onto terminals Y and X.Pulse goes from X to meter 30 through D-3 and C7 to Y.

0-3 which had collected charge while TR-l was closed, now dischargesthrough R-17, R8 and R12, to let positive reverse bias go back on baseof TR2 which goes back to cut-off. Negative is now back on base of TRlwhich saturates and recloses.

The system is now ready for the next pulse.

'The meter 30 is preferably DArsonval movement to provide an integratingaveraging of the pulses from the monostable multivibrator consisting ofTR-l and TR-2.

The time constant of the multivibrator is short enough to enable TR-land TR-2 to go back to original conditions before condensers C2 and 0-5will be recharged for the operating frequency or speed for which themeter is being used.

As TR-l recloses, terminal Y goes more positive and the positive pulsegoes from Y through C-7 and D-2 to terminal X, without going through themeter. Thus, the multivibrator doesnot cause a reading upon originalclosure of switch SW-l, but only upon actuation of the light cell.

To provide temperature compensation, the diode D-1 is employed as partof a voltage divider with R-8 and R12. As the ambient temperatureincreases, the resistance of D-l decreases and varies the bias on thebase of TR-Z. The condenser C-4 provides an A.C. by-pass circuit.

3 In order to provide a dual scale on the meter 70, the circuitry may bemodified as shown in FIGURE 3. A selector switch 75 controls thecircuitry to select the speed reading range desired. The meter readsboth positive and negative-going excursions of the pulses.

The instrument may be readily calibrated with any commercial fluorescentlight. Since the light intensity changes 120 times per second on regularcommercial lines, the photo-cell or eye, if pointed at such a light,will see 7200 pulses per minute. For a rotating device with one marker,that same scale reading would represent 7200 rpm. With two markers beinglooked at, that reading would represent 3600 rpm. By increasing thenumber of marks used on a moving object, a scale with a larger range maybe used to measure a relative small speed.

The tachometer disclosed herein thus provides a simple portable device,for measuring speed over a large range, by suitably preparing the movingobject to create the light pulses to the photocell. The use of themonostable multivibrator provides an independent pulse shaping andsizing circuit that eliminates error by making the pulses to the meterall of the same duration so the averaging process will be significant.The buffer circuit between the bridge and the monostable multivibratorpermits each to function independently according to its own timeconstant.

The circuitry may be modified without departing from the spirit andscope of the invention as set forth and defined in the claims. Thevalues of parameters shown represent a set with which the systemoperated according to the invention.

What is claimed is:

1. A speed-measuring apparatus, comprising:

a meter having a current coil and a movable pointer and a co-operatingscale calibrated to indicate speed units, and depending upon thefrequency and energy content of energizing pulses supplied to the coil;

a battery, a battery circuit having a pair of buss lines to be energizedfrom said battery as positive and negative buss lines, and a manuallyoperable switch to connect the battery to said battery circuit;

a lamp manually operable to direct an incident light beam onto a movingobject, to be reflected by and from a specific selected area of saidmoving object as periodic reflected light pulses;

a light cell to receive and be illuminated by such reflected periodiclight pulses, and said light cell being characterized by a highresistance when not illuminated and by a low resistance when soilluminated;

a normally balanced Wheatstone bridge arrangement with four impedancearms connected to said battery circuit and containing said cell as onearm, and having two normal balance points with a capacitor connectedbetween said two balance points of the bridge to receive a charge whenthe cell is illuminated and the bridge thereby unbalanced;

a sensing first transistor connected to and energized from said batterycircuit through its emitter and collector electrodes;

circuit means connecting the Wheatstone bridge capacitor to the baseelectrode of said sensing transistor, and normally biasing said sensingtransistor to open condition;

a switching second transistor connected to said battery circuit throughits emitter and collector electrodes, and means normally biasing saidsecond transistor to open condition;

circuit means including a capacitor and a resistor serially connectingsaid sensing first transistor collector terminal to said switchingsecond transistor base terminal;

an output pulsing third transistor connected to said battery circuitthrough its emitter and collector terminals;

a voltage-divider circuit connected to said battery circuit to provide apotential bias point connected to the base terminal of said output thirdtransistor to impress forward bias on the emitter base circuit of saidoutput third transistor to normally bias said output third transistor toclosed condition;

means connecting said switching second transistor to saidvoltage-divider circuit to shift the operative I potential impressedonto the base terminal of said output third transistor to establishbackward bias on the emitter-base circuit of said output thirdtransistor upon operation of said switching second transistor by saidsensing first transistor;

a first electrical load circuit connected to and extending from theemitter terminal of said output third transistor through the operatingcoil of said meter, and thence through a forward oriented first diodeand a capacitor to the collector electrode of said output thirdtransistor, to transmit a pulse through the meter coil when said thirdpulsing transistor is opened;

and a second diode connected to bridge the meter and said first diode,and oriented reversely to said first diode, to provide a discharge pathfor the capacitor when said output third transistor is closed;

said second transistor and said third transistor serving and functioningas a monostable vibrator to cause said pulses to the meter coil tobesubstantially uniform in duration and energy content.

2. A speed-measuring apparatus, as in claim 1, in which the junctionbetween said capacitor and said resistor in the coupling circuit betweenthe sensing first transistor and the switching second transistor iscoupled to one side of the battery circuit through a reverse bias diode,and is coupled to the collector terminal of the output third transistorthrough a feedback circuit including a resistor and a capacitor.

3. A speed measuring apparatus for measuring the speed of a moving body,by measuring the frequency of light pulses reflected from a selectedregion of the surface of said moving body as a consequence ofimpingement of an incident light beam associated with said measuringapparatus and directed at said moving body to strike said selectedregion, said speedmeasuring apparatus comprising:

a voltage supply source;

a pair of buss lines to be energized from said source as positive andnegative buss lines;

a lamp to serve as a source of light beam to be directed at the movingbody that is to be measured for speed;

a thumb switch to be operated by an operator handling said apparatus,and serving when operated, to connect said source to said lamp and tosaid buss lines;

an electrical four-arm bridge of two circuits with two impedanceelements serially joined in each circuit to provide an intermediatejuncture and both circuits being connected in parallel between said twobuss lines and characterized to be normally electrically balanced sothat the two junctures in the two circuits are normally ofequi-potential, said bridge containing a light-responsive element in onearm as an impedance element to be normally of high resistance when notilluminated but dropping to a low resistance value when illuminated by alight beam reflected from said selected region of said moving body, tothereby unbalance said bridge and change the equipotential relationbetween said two junctures, to establish a potential differencetherebetween;

a sensing capacitor electrically connected to and between said normallyequi-potential juncture points of said electrical bridge and serving toreceive a charge from said potential difference upon unbalance of saidbridge resulting from illumination of said light-responsive element bysuch light beam reflected from said moving body;

a buffer transistor having emitter and collector electrodes respectivelyconnected through resistors to the positive and negative buss lines, andhaving a base electrode;

means connecting said base electrode of said bufier transistor to one ofsaid intermediate junctures to thereby normally bias said buffertransistor to an open condition when said bridge is balanced and to biassaid bufler transistor to a closed condition when said bridge isunbalanced;

a monostable multivibrator trigger circuit including an input switchingtransistor and a controlled output pulsing transistor, each having anemitter and a collector terminal;

means connected to said buffer transistor for impressing input pulsesonto said input transistor of said mono-stable multivibrator to initiateoperation of said mono-stable multivibrator once each time said bridgebecomes unbalanced;

and a meter circuit connected across and between the emitter and thecollector terminals of said output pulsing transistor to receive andaverage pulses from said output pulsing transistor and to indicate thefrequency of said pulses.

4. A speed measuring apparatus, as in claim 3, in

which in a forward direction from said output transistor through themeter in such forward biassed direction, and said meter coil circuitalso includes a reverse biassed diode connected to electrically bridgethe meter coil and the forward biassed diode, said reverse biassed diodeserving to by-pass around said meter coil and forward-biassed diode anyenergy pulse of opposite polarity from said output pulsing transistor.

5. A speed measuring apparatus, as in claim 4, in

which said monostable multivibrator includes:

a voltage-divider circuit connected to and between the two buss linesand providing an intermediate terminal point connected to the baseterminal of said output pulsing transistor to establish a forward-biaspotential in the emitter-base circuit of said output pulsing transistorto cause immediate saturation and closing operation of said outputpulsing transistor immediately upon energization of said buss lines uponclosure of said thumb switch by the operator, in order thereby toshort-circuit said meter coil circuit immediately and preventenergization of said meter coil until a signal pulse is impressed on thebase terminal of said output pulsing transistor.

6. A speed-measuring apparatus, as in claim 5, in which said inputswitching transistor has its emitter connected to the positive buss linethrough an emitter resistor, and has its collector connected to thenegative buss line through a collector resistor, and has its baseterminal connected to a circuit normally energized to bias saidswitching transistor to open condition.

7. A speed-measuring apparatus, as in claim 6, in which said means forimpressing input pulses onto said input transistor of said monostablemultivibrator comprises:

a coupling circuit, containing a capacitor and a resistor,

connected in that sequence, from the collector terminal of said buffertransistor to the base terminal of said input switching transistor.

8. A speed-measuring apparatus, as in claim 7, including a diodeconnected in reverse polarity direction between the positive buss andthe junction point between the capacitor and the resistor of saidcoupling circuit between said buffer transistor collector and saidswitching transistor base;

a feed-back capacitor and resistor circuit connected from the outputtransistor collector to said input junction point to which said diode isconnected;

and a capacitor connected between the input switching transistor baseand the positive buss.

4/1948 Hammond. 4/1964 Nelson.

FOREIGN PATENTS 1,018,660 10/1950 Germany.

RUDOLPH V. ROLINEC, Primary Examiner.

M. J. LYNCH, Assistant Examiner.

1. A SPEED-MEASURING APPATATUS, COMPRISING: A METER HAVING A CURRENTCOIL AND A MOVABLE POINTER AND A CO-OPERATING SCALE CALIBRATED TOINDICATE SPEED UNITS, AND DEPENDING UPON THE FREQUENCY AND ENERGYCONTENT OF ENERGIZING PULSES SUPPLIED TO THE COIL; A BATTERY, A BATTERYCIRCUIT HAVING A PAIR OF BUSS LINES TO BE ENERGIZED FROM SAID BATTERY ASPOSITIVE AND NEGATIVE BUSS LINES, AND A MANUALLY OPERABLE SWITCH TOCONNECT THE BATTERY TO SAID BATTERY CIRCUIT; A LAMP MANUALLY OPERABLE TODIRECT AN INCIDENT LIGHT BEAM ONTO A MOVING OBJECT, TO BE REFLECTED BYAND FROM A SPECIFIC SELECTED AREA OF SAID MOVING OBJECT AS PERIODICREFLECTED LIGHT PULSES; A LIGHT CELL TO RECEIVE AND BE ILLUMINATED BYSUCH REFLECTED PERIODIC LIGHT PULSES, AND SAID LIGHT CELL BEINGCHARACTERIZED BY A HIGH RESISTANCE WHEN NOT ILLUMINATED AND BY A LOWRESISTANCE WHEN SO ILLUMINATED; A NORMALLY BALANCED WHEATSTONE BRIDGEARRANGEMENT WITH FOUR IMPEDANCE ARMS CONNECTED TO SAID BATTERY CIRCUITAND CONTAINING SAID CELL AS ONE ARM, AND HAVING TWO NORMAL BALANCEPOINTS WITH A CAPACITOR CONNECTED BETWEEN SAID TWO BALANCE POINTS OF THEBRIDGE TO RECEIVE A CHARGE WHEN THE CELL IS ILLUMINATED AND THE BRIDGETHEREBY UNBALANCED; A SENSING FIRST TRANSISTOR CONNECTED TO ANDENERGIZED FROM SAID BATTERY CIRCUIT THROUGH ITS EMITTER AND COLLECTORELECTRODES; CIRCUIT MEANS CONNECTING THE WHEATSTONE BRIDGE CAPACITOR TOTHE BASE ELECTRODE OF SAID SENSING TRANSISTOR, AND NORMALLY BIASING SAIDSENSING TRANSISTOR TO OPEN CONDITION; A SWITCHING SECOND TRANSISTORCONNECTED TO SAID BATTERY CIRCUIT THROUGH ITS EMITTER AND COLLECTORELECTRODES, AND MEANS NORMALLY BIASING SAID SECOND TRANSISTOR TO OPENCONDITION; CIRCUIT MEANS INCLUDING A CAPACITOR AND A RESISTOR SERIALLYCONNECTING SAID SENSING FIRST TRANSISTOR COLLECTOR TERMINAL TO SAIDSWITCHING SECOND TRANSISTOR BASE TERMINAL; AN OUTPUT PULSING THIRDTRANSISTOR CONNECTED TO SAID BATTERY CIRCUIT THROUGH ITS EMITTER ANDCOLLECTOR TERMINALS;